Control apparatus



CONTROL A.PPAM'UIS Filed nec. 19, 1934 l 2 sheets-sheet 1 s; V ha A TTORNEV June 23, 1936. P. P. cloFFl 2,045,438

CIONTROL APPARATUS Filed Dec'. 19, 1934 2 sheets-sheet 2 A T TORNEY loV - the main paper drive drum and driven by the' Patented .y June 23, 1936 CONTROL APPARATUS Paul P. Ciofl, Brooklyn, N.-,Y., assignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of` New York i Application December 19, .1934, Serial No. 758,170

l0 Claims. (Cl. 236446) This invention relates to apparatus for the automatic control of furnace heating or cooling rates. In many cases during heat treatment of metal it is desired to have control of the heating or cooling rates.

'I'he object of this invention is to provide an improved and simple arrangement for producing aprogressive change of temperature, with time, according to a predetermined program. I

Temperature recorders which plot temperature changes, with time, are often' mod iiied to include means vfor controlling the temperature of a furnace.- It is common practice to have the means f or controlling the temperature comprise a pair of contacts actuated by the mechanism which records the temperature and to have the contacts control the supply of current to a heating coil in the furnace. When the contacts are closed the furnace absorbs more power. When the contacts are open the power to the furnacevis diminished or discontinued. ,If the temperature of the furnace falls below a set value, the contacts are automatically closed and the furnace absorbs more power. A rise in temperature above another set value causes opening of the contacts. Thus, the

temperature is held between narrow limits over any required period of time.

In accordance with this invention, the temperature setting for the make-and-break of the contacts is made to change with time to `correspond to a desired heating or cooling curve whereby the rate of heating or cooling of the furnace is controlled.

More speciiically, the temperature recorder, which may be of the well-known Leeds and Northrup type, is provided with an auxiliary paper drive drumpreferably located in front of same worm. This auxiliary drum drives a program sheet comprising a length of recorder paper on which is pasted a strip of foil, one edge of which corresponds to a predetermined heating or cooling rate. Electric contact is maderwith this edge of the foil by a metal stylus pressing lightly on the program sheet. The stylus and metal foil are connected by flexible leads to one end of a double-pole-double-throw switch, while the usual Acontrol contacts for constant temperature are When heating or cooling is to be at a controlled rate a paper with that heating or cooling curve upon it is adjusted on the auxiliary drum at the proper place. The switch is thrown to connect the stylus and foil in circuit with the power con- 5I -trol relay. The temperature \of the furnace is then controlled by the stylus and the foil on the control sheet and as the foil is always moving linearly with time, the temperature at which the shift between .power limits takes place thus 10 varies with time. The result is that the temperature ofy the furnace changes in accordance with the predetermined heating or cooling rate, the

rate being determined by the location and form 'of the edge of the metal foil.

Instead of securing a strip of metal foil on the control sheet, the same result would be secured by'providing an elongated aperture in the paper whereupon the stylus wouldmake electrical contact with the` auxiliary drum along the edge of zo ythe aperture in the paper.

`In the drawings:

Fig. 1 is a view in perspective of the apparatus for controlling the supply of current to a heating element, in accordance with a predetermined 25 program, combined with apparatus for graphically recording temperature. This iigure also 'includes a'schematic showing how thegcontrol apparatus andthe recording apparatus/may be associated with a heating element; s Fig. 2 is a View in perspective of the control apparatus and the temperature recording apparatus shown in Fig. 1 and including some of the mechanical structure of the temperature recorder;

Fig. 3 is a top plan view of a portion of a control sheet for the control apparatus; and

Fig. 4 is a view of a record sheet made by a recorder when the control sheet is used having the program shown in Fig. 3, the record sheet be- `40 ing superimposed on the control sheet shown in Fig. 3. l

As stated in connection with the heat treatment of metal or other substances, it becomes necessary in some instances in order to obtain '45 articles having required characteristics, to not only bring the article treated to a required temperature, but to bring the article to the required temperature within the space of a certain predetermined period of time. In some cases it also becomes necessary in order to obtain articles having required characteristics to control the rate of cooling the article after it has been brought to a required temperature.

In the heat treatment of articles in electric furnaces, it has been the practice to manually connect the source of current supply to a heating element in the furnace at the beginning of the heat treatment andto thereafter manually control the supply of current to the heating element in accordance with a predetermined program. This requires constant supervision of the operation of the furnace and the result obtained depends on the faithfulness of an attendant in manually controlling the operation of the furnace. `If the supply of current to the heating element in the furnace is not manually controlled by the attendantexactly in accordance with a predetermined program, the article treated will not have the required characteristic. For instance, in the heat treatment of a piece of magnetic material, it may .be necessary in order to obtain a piece of material having the required characteristic, to bring the temperature of the furnace in which the article is being treated up to a predetermined level Within a certain predetermined period of time, to hold the furnace at that temperature for a certain length of time and then have the furnace cool off down to room temperature within acertain predetermined period of time. Y

Withthis invention the human element may be eliminated from the control of the furnace from the time'in which an article is' placed in a furnace and the current lis turned on until the heat treatment is finished, or during any part or parts of the heat treating program. AThe heating or cooling rates or both the heating and the cooling rates of the furnace may be automatically controlled in accordance with a predetermined program. Graphic records made in experimental heat treatments may be utilized as patterns for control sheets for controlling the supply of current to a heating element in a furnace.

Although it is not essential to this invention, the control apparatus may be used in connection with a modified well-known type of temperature recorder. To illustrate"y the invention and to show one Way in which it may be-used, the invention is shown in the drawings and is described`in this specification as being applied to a temperature recorder of theLeeds and Northrup type.

Referring to the drawings in which like reference characters designate the same parts in the several views, I is the temperature recording apparatusv and 2 is the control apparatus. The temperature recording apparatus I is adapted to make a graphic record of the temperature of a furnace 3 which is shown in the schematic portion of Fig. 1. 'I'he furnace 3 includes a heating coil 4 which is supplied with currentfrom a suitable source such, for instance, as the alternating current generator 5 over the conductors 6 and 1. A circuit including the source of alternating current 5 and the heating coil 4 includes an armature 8 and a front contact 9 of an electromagnetic device I0. The electromagnetic device Il) is in a circuit II which may be brought under the control of either the temperature recordingl apparatus I or the temperature control apparatus 2 by manual operation of a double-pole-doublethrow switch I2. When the switch I2 is throwncircuit I I is brought under the control of the temperature control apparatus 2. The circuit II includes a source of current supply such, for instance, as the battery I5, conductors I6 and I1,

electromagnetic device I and the central polesY of the switch I2. In shunt across 'the conductors 1 I6 and I1 are a resistance I8 and a condenser I3 connected in series.

The temperature of the furnace 3 is measured in the usual manner by a thermocouple 20', the electromotive force of which is adapted to be balanced against the potential difference across the portion of a resistance element 2 I. 'I'he potential difference across the resistance element 2| is maintained constant by a potentiometer circuit comprising a battery 22, a fixed resistance 23 and a variable resistance 24 which is provided for the purpose of adjusting for the variations of the electromotive force of the battery 22. When the electromotive force of the thermocouple 2|] is equal to the potential difference across the resistance element 2 I between the point 25 and the sliding contact 26, no current will flow in a galvanometer 21 which is included in the thermocouple circuit. Whenever there is a difference between the electromotive f /rce of the thermocouple 20 and the potential ifference across the resistance element 2l between the point 25 and the sliding contact 26, a current will iiow through the galvanometer 21 and deflect a needle 28 attached thereto, asshown in Fig. 2, either to the right or to the left, depending upon whether the electromotive force is greater or less than the potential difference across the portion of the resistance element 2l between the point 25 and the sliding contact 26. 'Ihe deflection of the gal- 4vanometer needle 28 causes a rotation of the shaft tion of the needle 28 beyond ends of the ledge 30. The ledge 30 is fixed to a U-shaped yoke 32 pivoted at 33-33. The yoke 32. carries a down-` wardly extending arm 34., the lower end of which is bent outward and then inward and upwardly to form a U-shaped end which is engaged by a cam 35 mounted on a shaft 36 which is continuously -rotated by a motor 31 causing a rising and falling of the yoke 32 and the ledge 30 and imparting a similar movement to the end of the needle 28 which rests on the ledge 30. A resilient arm 38 attached at its upper portion to a support, not shown, extends downwardly from a point directly below the center of the yoke 32 and below the ledge 30. The arm 38 is engaged by a secondcam 39 on the shaft 36 which tends to move continuously the arm 38 toward and away from a disc 4I). To the lower end of the arm 38 is pivotally attached a cross-arm 4I which carries at its extremities a pair of shoes 42 adapted to frictionally engage the disc 40 when the arm 38 is moved toward the disc. The

cross-arm 4I terminates in a pair of projec tions 43 located in such a position that a pair of rotating cams 44 will not normally strike them. A plate 45 having downwardly diverging arms is fixed to the cross-arm 4I and carries a pair of pins 46 which project normal to the plane of 70 the plate 45 and which are engaged by spaced and downwardly projecting arms 41. The arms 41 are pivoted at 48 and are provided with upp'er and inwardly directed projections 49 which project over the ledge 30. The arms 41 have 75A Cil the cam 39 will act to allow/the shoes 42 to fric? tionally engaged the disc and as the cam 44 is rotated, it will engagea projection 43 and return the cross-arm 4| to normal horizontal position. The shoes 42 will grip the disc 40 and rotate the disc thereby rotating the shaft 29, to adjust the resistance element 2| to such a value as to cause the galvanometer needle 28 to return to its central position indicating that the voltage of the thermocouple is equal to the potential difference across the portion of the re sistance element 2l between the point 25 and the sliding' contact 26.

Secured upon the shaftk 29 is also a grooved pulley 5I around which, as shown in Fig. 1, passes a cord 52 whichpasses over suitable pulleys 53 and is secured to a carriage 61 carryjing a marker pen'54 movable transversely with respect to the recorder paper 55 which passes over and is driven by a drum 56. The drum 56 is continuously rotated through suitable worm gearing by means of the motor 31. The marker pen 54 makes @continuous line on the recorder paper 55 and is moved transversely, whenever the shaft 29 is rotated,` due to deflections of the galvanometer needle 28 and the adjusting movements of the resistance element 2l;

Attached to the shaft 29 is a cam 51 operates a pair of contacts 58. The contacts 58 are wired to the right-hand poles of the switch I2. When the switch I2 is thrown to the right and engages the right-hand poles I3, the current supplied to the heating coil 4 in the furnace 3 is under the control of the recording apparatus I. When the shaft 29 is rotated, it causes the cam 51 to close the contacts 58, the electromagnetic device I0 is energized and pulls its armature 8 against front contact 9. This closes a circuit to the heating coil 4 and heat is applied to the furnace 3. When the thermocouple 20 in the furnace becomes sufficiently aifected by the increase in temperature in the furnace as to cause unbalance in the circuit including the resistance element 2I and the shaft 29 is rotated, the cam 51 operates to release the contacts 58. The electromagnetic device I0 is then deenergized and releases its armature 8 from contact with front contact-9. The current supply circuit for the heating coll 4 is then opened and remains open until the temperature of the furnace drops to a sufciently low level to affect the thermocouple 26 to cause an unbalance in the circuit again. In this instance the gaivanometer needle 28 is deflected to a point opposite to that which it assumes for high temperatures. 'Ihe shaft 29 is rotated in the direction opposite to its previous movement and the cam 51 closes the contacts 56. The electromagnetic device IU is then again energized and current is supplied to the heating coil 4.

From the vforegoing description it is obvious that with the switch I2 thrown to the right and the current supply to the heating coil 4 under the control of the recorder apparatus I, a constant predetermined temperature within certain-allowed limits will be maintained in the lfurnace 3. With this apparatus controlling the which cooling rate program for the furnace 3, the length and theform pi' the line 6I having been predetermined by experimentaltests or by calculation. The line 6I may be a slit in the control sheet 60 or a strip of conducting material incorporated therein. A convenient way of providing the line 6I 1in the control sheet 60 is to draw a line of the required length and form on n the control sheet 60, then cut through the control sheet 69 .along the line marked thereon. yThe slit cutv through the control sheet 60 may then be widened by cutting away more ofthe paper along a line substantially parallelto the line 6I, but not changing the length or the form of the slit rst cut in the paper since this rst cut contains an edge which is the control line required forr the heating or the cooling rate program. Thedrum 59 is rotatably supported in a frame 62 which may be part of the recorder frame and carries at one end a worm wheel 63. The worm wheel 63 is driven by a worm 64 connected to a shaft 65 anddriven through a suitable system of gears by the motor 31. The shaft 65 which is part of the drum drive mechanism in the recorder I may be utilized as shown in the drawings, to drive both the recorder drum 56 and the drum 59 of the control apparatus 2, the

worm 64 on the shaft 65 being placed between a worm wheel 66 on the recorder and the worm wheel 63 of the control apparatus 2.

Supported on the carriage 61 carrying the recorder pen 54 is an arm 66 which is connected by means of a universal connection 69 to a stylus arm 10. The stylus arm 16 carries at its free end a stylus holder 1I carrying an adjusting screw 12 and an adjustable stylus contact 13 which is adapted to bear against the control sheet 60 or project through the slit in the con- -trol sheet 60 according to the position taken.

'I'he lower extremity of the adjustable stylus 13 is rounded so that it will readily slide over the edge of the slit cut along the line`6I when the carriage 61 is moved transversely by means of the cord 52 and the grooved pulley 5I.' The stylus arm 10 is connected by a conductor 14 to the lower left-hand pole I4 of the switch I2. The upper left-hand pole I4 of the switch I2 is connected by conductor 15 to the frame 62.

When th'e switch I2 is thrown to the left and engages the poles I4, the current supply for the heating coil 4 of the furnace 3 is controlled through the stylus 13 and the drum 59 or the conducting strip on the controlsheet 60 of the control apparatus 2. When the stylus projects through the slit in the control sheet 60 and engages the drum 59, the electromagnetic device I 0 is energized and closes its armature 8 against front contact 9 to complete the circuit of current supply to the heating coil 4. When the paper of the control sheet 60 comes between the stylus 13 and. the drum 59, the circuit to the electromagnetic device I0 is opened. The electromagnetic device I0 releases and the circuit to the f provided. The line 6I represents a heating or heatingcoil 4 is opened by release of armatureIl .9 from engagement with front contact 9. f Withthearrangement shown in Figs. 1 and 2, the drum 59 of the control apparatus 2 is driven 5 in a clockwise direction and 'the drum` 55 of the recording apparatus is driven in a counter: clockwise directioni. 'I'he record of the gradufally rising temperature of the furnace 3 on the record sheet 55, therefore, will slope upward toward the right on the record sheet 55. 'I'he program curve,A on the control sheet 60 will slope downward towardthe right of the control sheet 60. As the roller 59 moves the control sheet 60 under the stylus 13, it brings the slit in the paper of the control sheet 60 under the stylus 13. The stylus 13 then makes contact with the metal drum 59. This result s in energization of the electromagnetic device I0 and pomrection of the supply of current tothe heating coil 4 of the 2d furnace 3. 'I'he furnace 3, therefore, begins to heat. The thermocouple then becomes affected and unbalance occurs in the thermocouple circuit. The galvanometer needle 28 is then deected. The rising yoke 32 by means ofthe ledgev 30 moves the needle 28 upward against one of the projections 49 and causes the corresponding varm 41 pressing against the pin 46 to swing the -plate 45 and the cross-arm 4| about the common pivot point of the plate 30 45 and the cross-arm 4|. This will Vbring a projection 43 into the path of movement of a cam 44 which is continuously rotating. The cam 39 on the continuously rotating shaft 35 is positioned so that it releases the resilient arm 33 when the enlarged portions of the cams 44 are down and permits the vshoes 42 to frictionally engage the disc 4|l. One of the cams 44, therefore, will press against a projection 43 and restore the cross-arm 4| to normal horizontal position. The disc 40 will be rotated by means of a shoe 42 and will rotate the shaft 29 to adjust the resistance element 2|. Rotation of the shaft 29 will cause rotation of the grooved pulley 5|, movement of the cord 52 and transverse 45' movement of the carriage 61. The recorder pen 54, therefore, will be movedv transversely to the right on the recorder paper and the stylus 13 will be moved transversely to the right of -the control paper until it passes over the right- 50 hand edge of the slit'in the control sheet-90 and on to the paper of the control sheet. The electromagnetic device IU will then be deenergized and will open the circuit to the heating coil 4l of the furnace 3. .The furnace 3 then begins to cool. As the furnace cools the thermocouple 20 becomes affected, rotation of the shaft 29 takes place and the stylus 13 is moved back again to the left to project through the slit in the control sheet 60 and make contact with the drum 59. 60' Since the drum 59 of the control apparatus 2 is continuously rotated and carries the control sheet 60 relative to the stylus 13, new portions of the program curve are continually being presented to the stylus 13. 'I'he paper portion of the control sheet 50 along the program curve L The program line 9| on the control sheet Il may be made to have any slope and shape required for a required heat treatment program. The control sheet 60 may include al program line for controlling heating of the'furnace, cooling of the furnace, maintenance of a required temperature, or any part or parts of the programs above mentioned and required.A For instance, in Fig. 3 the control sheet 50 includes a program in which the-.furnace would be gradually brought l0 to a required comparatively high temperature in .a predetermined period of time, then 'maintained at the comparatively high temperature for a predetermined period and then gradually cooled to normal or room temperature in a predetermined l5 period of time. At the top of the control sheet 5|! the program line 6| slopes downward toward the right and terminates in a comparatively straight portion which extends downward along the control sheet and'into a portion which slopes 20 downward and toward the left of the control sheet. The upper portion of the program line 6I is a program for gradually heating the furnace, the comparatively straight downwardly extending portion is the program for maintenance at 25 the required temperature for a predetermined period of time and the lower portion of the program line 6| which slopes toward the left of the control sheet 60 is a program for gradually reducing the temperature ofthe furnace. 30 'I'he slitinthe control sheet 50 'may be filled fwith a conducting strip to provide a contact strip between the stylus 13 and the drum59 and to prevent displacement of the side` edges of the slit by the stylus 13.. In Fig. 3 a conducting strip 35 15 which may, for instance, be a metal foil, is pasted to the under-surface of the control sheet 60. The conducting strip J6 is wider than the slit in the control sheet and follows the general shape of the slit in the control sheet. The o conducting strip 19, however, could be simply a rectangular sheet of conducting material of the same length and width as the control sheet 60 and secured to the under-surface of the control sheet or could vbe of any size and form suf- 45 iicient to cover the portions of the control sheet 60 traversed by the program line.

A heat treatment record made by the recorder A apparatus when the control apparatus 2 is emas it would appear if placed beneath the record 55 sheet 55. Where the record lines cross into the slit in the control sheet 50, current is supplied to the heating coil of the furnace. Where the record lines pass over on to the paper adjacent the slit,

. no current is/supplied to the heating coil.

While .this invention has beendescribed and referred to as apparatus for controlling the temperature of a furnace, it is also applicable to the control of other conditions such, for instance, as chemical, physical or electricaly the magnitude of 65 the conditions being controlled by the apparatusv in accordance with a predetermined program. The control apparatus may be made to operate to change the application of current, heat, chemical, or some other agent or reagent whenever there is a deviation from a predetermined condition with time.

Since the essential elements of the apparatus of my invention consist of a program sheet which controls the apparatus in accordance with a pre- 7.57-

determined program, the sheet containing a metallic surface in the form of a curve which represents the changes required with time and the sheet affects the stylus or contact member bearing on the sheet, the stylus and metal portions of the sheet -being in a circuit which includes means to affect the apparatuswhich controls the condition, therefore, by replacing a control sheet containing one program by a control sheet con-y taining another program, any desired condition may be produced, changed and controlled.

What is claimedis:

1. In a current control for an electrical element, a control sheet having 'formed therein an elongated aperture of a predetermined form and edge portions of said control sheet along said aperture being curved in accordance with a current supply program for said element.

2. A current control for an electrical element comprising, in combination a pair of contacts and a control sheet operating between the. contacts,

` said control sheet having formed therein an elongated aperture of a predetermined form and an edge portion of said control sheet along said aperture curved in accordance with a current supply program for said element.

3. A current control for an electrical element 'Y comprising, in combination a driven contactpa reciprocating contact, means to drive the driven contact, means to move said reciprocating contact, a control sheet operating between said contacts, said control sheet having provided therein an elongated aperture of a predetermined form to permit said reciprocating contact to engage said driven contact, said control sheet lbeing driven by said driven contact and an edge portion of said control sheet along said aperture formed in accordance with a current supply program for said electrical element.

4. A current control for an electrical element, comprising, in combination, a driven conducting drum, means to drive said drum, a metal stylus, a sheet of insulating material driven by said 'drum between saiddrum and' said metal stylus, said @sheet of insulating material having formed therein an elongated aperture of a predetermined Y form and one edge of said ,control sheet along said laperture containing a series of curves representing a current supply program for the electrical element.

5. -In a current control for an electrical element, a control sheet of insulating material having formed therein an elongated aperture, a stripv of conducting material adjacent said control sheet and bridging all portions of the aperture therein and an edge portion of said control sheet along said aperture comprising a predetermined system of curves.

` .6. A current control for an electrical element comprising a pair of contacts, a control sheet oi!` insulating material operating between said contacts, an elongated aperture formed in said conslightly above the plane of said conducting strip.

'7. In a control for a heating element, a source of current for the heating element, a pair of contacts, a circuit including said heating element and said contacts, and an insulating control sheet operating between said contacts, said control sheet having formed therein an elongated aperture in the form of a curve representing the rate at which current is to be supplied to said heating element.

8. In a temperature control apparatus, a con tinuously driven drum, a temperature control program sheetdriven by said drum, a stylus bearing on the program sheet, a carriage for said stylus, a movable structure responsive to temperature changes and controlling the movement of said carriage, said program sheet having a metal foil strip adhesively secured thereto having a wave-line edge which represents the program, a heating circuit, and a relay controlling said circuit and in circuit with said stylus and said metal foil strip. 9. InxaI temperature control apparatus, a continuously driven drum, driven at a constant speed, driving means for `said drum, a temperature control program sheetA driven by said drum,l a metal stylus resting on said program sheet, a reciprocating carriage supporting said stylus, apparatus responsive to temperature changes for causing reciprocating movements of said car- 3 tion, amovable structure controlled by said galvanometer, a carriage moved thereby; a stylus on said carriage, a continuously driven drum,a program sheet of insulating material driven by said drum and engaged by said stylus, said program sheet being provided with conducting means outlined by portions of the insulating material in wave-line form which determines the application of the program to the apparatus for producinga change in the condition, and means in circuit with the stylus and last mentioned means for controlling said apparatus to produce the change according to the rate as determined by the program sheet.

` i' PAUL P. CIOFFI. 

